KR20240164677A - Method of preparing pyrolysis fuel oil from waste plastics - Google Patents

Abstract

The present invention provides a method for producing waste plastic pyrolysis oil, comprising: (S1) a step of introducing waste plastic raw materials into an upper feed port of a tubular reactor including multiple zones separated vertically and pyrolyzing them; (S2) a step of condensing a gaseous stream produced in the step to obtain liquid oil; and (S3) a step of purifying the liquid oil, wherein the pyrolysis is performed under conditions of increasing temperature from an upper zone to a lower zone of the tubular reactor.

Description

{METHOD OF PREPARING PYROLYSIS FUEL OIL FROM WASTE PLASTICS}

The present invention relates to a method for producing pyrolysis oil from waste plastic, and more specifically, to a method for producing light hydrocarbon oil at a high yield by improving the pyrolysis efficiency of waste plastic.

Recently, the development and use of plastics with properties required for various purposes and purposes is increasing. Plastics use a lot of energy from crude oil extraction to manufacturing, and a large amount of carbon is emitted in the process. Furthermore, when plastics used in various products are discarded, environmental pollution and enormous processing costs occur, so recycling of waste plastics is becoming an important social issue.

In general, there are three methods for recycling waste plastics (resins): mechanical recycling, chemical recycling, and thermal recycling. Mechanical recycling is a method in which the collected waste plastics are crushed and sorted to separate the waste plastics by type, and then melted and pelletized using an extruder, and then mixed with new materials at a certain ratio or functional additives are added to manufacture resin products. Chemical recycling is a method in which only specific polymers are extracted or pure single molecules are recovered and re-polymerized using various chemical means. Thermal recycling is a method in which waste plastics are burned to recover heat energy.

In particular, the above chemical recycling can reduce greenhouse gases compared to incineration of waste plastics and has recently attracted attention in terms of developing alternative fuels.

For example, when waste plastics such as polyethylene or polypropylene are heated and pyrolyzed at a certain temperature, a gaseous stream mixed with non-condensable gas and liquid oil is generated, and highly viscous residual wax that is not completely decomposed may be discharged. Among the pyrolysis products, the liquid oil is increasingly important as fuel oil for the production of petrochemical products, and therefore, research is actively being conducted to increase the yield of the liquid oil.

The liquid oil produced from the pyrolysis of the above waste plastic, i.e., pyrolysis oil, is typically a mixed oil containing light hydrocarbon oils of C _5-12 such as naphtha and hydrocarbon oils of longer chains. If the mixed oil contains a large amount of high-boiling-point (heavy) components, the yield of high value-added light hydrocarbon oils is limited, and there are problems in that the amount of heavy oil components produced and the amount of wax residue discharged are excessive.

To solve these problems, methods have been proposed to perform a contact decomposition reaction by catalytic cracking during the pyrolysis of waste plastics, or to condense heavy hydrocarbon (i.e., long-chain hydrocarbon) components among the pyrolysis products of waste plastics using a contactor and then circulate them to a pyrolysis reactor to undergo the pyrolysis process again. However, these methods have limitations in increasing the pyrolysis efficiency of waste plastics, and are limited to recycling as mixed oil.

Therefore, a technology is needed to improve the pyrolysis process of waste plastics to increase the yield of advanced light hydrocarbon oil.

United States Patent Application Publication No. US2012/0261247

The problem to be solved in the present invention is to solve the problems mentioned in the background technology of the above invention by performing pyrolysis of waste plastic under elevated temperature conditions rather than a single temperature in a vertically arranged tubular reactor, and securing sufficient residence time of the liquid component descending inside the reactor to improve the pyrolysis efficiency of waste plastic, thereby producing light hydrocarbon oil at a high yield.

According to one embodiment of the present invention for solving the above problems, a method for producing waste plastic pyrolysis oil is provided, comprising: (S1) a step of supplying waste plastic raw materials to a tubular reactor including multiple zones separated vertically to perform pyrolysis; (S2) a step of condensing pyrolysis gas produced in the step to obtain liquid oil; and (S3) a step of purifying the liquid oil, wherein the pyrolysis is performed under conditions of increasing temperature from an upper zone to a lower zone of the tubular reactor.

The tubular reactor may include a multitube falling-film evavorator and may be provided with external heating jackets of different lengths for each section.

According to the present invention, by supplying waste plastic raw materials into a tubular reactor including multiple zones separated vertically and continuously performing thermal decomposition by gradually increasing the temperature toward the lower zones, the decomposition efficiency of waste plastics can be improved, thereby increasing the yield of high-grade light hydrocarbon oil and minimizing the discharge of residual wax having low utilization.

In addition, by considering the viscosity of the liquid component descending in each section of the tubular reactor, external heating jackets of different lengths are provided to secure sufficient reaction residence time, thereby further improving the thermal decomposition efficiency of waste plastic.

Furthermore, the utilization of light hydrocarbon fuel oil obtained from the pyrolysis of waste plastic can reduce greenhouse gas emissions caused by the supply of raw materials for petrochemical processes, and improve process efficiency such as reducing energy consumption. In addition, it is also environmentally beneficial because no harmful gases are generated during the treatment of waste plastic.

Figures 1 and 2 schematically illustrate a process for performing pyrolysis of waste plastic using a tubular reactor including vertically separated sections in one embodiment of the present invention.

The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to explain his or her own invention in the best manner.

The terms “include” or “comprising” as used herein specify a particular characteristic, region, integer, step, operation, element, or component, but do not exclude the addition of any other particular characteristic, region, integer, step, operation, element, or component.

The term 'stream' used herein may mean the flow of fluid within a process, and may also mean the fluid itself flowing within a pipe. Specifically, the stream may mean both the fluid itself flowing within a pipe connecting each device and the flow of the fluid. In addition, the fluid may include at least one component of gas, liquid, and solid.

The term "C _n ", as used herein, refers to all hydrocarbons having n carbon atoms, for example, "C _5-12 " refers to all hydrocarbon molecules having 5 to 12 carbon atoms.

The term 'liquid oil' as used herein means the product obtained by converting the gaseous stream obtained in the thermal cracking step into a liquid phase by condensation, and may also be referred to as 'liquid distilled oil'.

Additionally, “pressure” as referred to herein means absolute pressure measured relative to a complete vacuum.

A method for producing waste plastic pyrolysis oil according to one embodiment of the present invention comprises (S1) a step of pyrolysis of waste plastic raw materials, (S2) a step of obtaining liquid oil by condensation, and (S3) a step of purification.

Below, the method for producing waste plastic pyrolysis oil according to the present invention is described in detail step by step.

First, waste plastic raw materials are prepared and fed into the feed port of a vertically arranged tubular reactor to perform pyrolysis (S1).

The above waste plastic may include natural polymers, synthetic polymers, or mixtures thereof, and the synthetic polymer may include thermoplastic resins such as polyethylene, polypropylene, and polystyrene. In addition, the thermoplastic resin may be mixed with other types of resins such as PVC, PET, and thermosetting resins.

After being collected and sorted, waste plastics of such materials may undergo a pretreatment process including shredding, washing, drying, and melting. The pretreatment process may be performed in a manner conventional in the art.

For example, the size of the waste plastic shredding is not particularly limited, but can be performed in a range of 0.5 to 6.0 cm, and the washed and dried waste plastic shredded material can be fed into a tubular melter such as an extruder to be melted. The extruder has a function of melting and kneading and extruding, and can be, for example, a twin-screw extruder. When the waste plastic is a thermoplastic resin, such as polyethylene, polypropylene, or a mixture thereof, the melting temperature can be, but is not limited to, 120 to 350° C. or 150 to 250° C.

In order to increase the thermal decomposition efficiency of the waste plastic melt obtained through the above pretreatment process, the present invention uses a tubular reactor including multiple vertically separated zones.

Typically, a tubular pyrolysis reactor has a structure in which the introduced raw material flows down by gravity inside a vertically erected tube and pyrolysis occurs along the inner wall, and the vaporized product from the pyrolysis is discharged to the outside through the upper part of the reactor.

For example, when the waste plastic raw material is fed into the upper feed port of the reactor and heated to perform thermal decomposition, the vaporized gas stream generated is discharged out of the reactor through the upper feed port of the tubular reactor, and the remaining liquid stream that has not yet been vaporized descends along the inner surface of the tubular reactor to perform additional thermal decomposition, thereby improving the decomposition efficiency of the waste plastic.

The heating of the waste plastic can be performed by passing high temperature/high pressure steam, hot water or heat transfer fluid through a jacket provided externally to transfer high temperature heat to the waste plastic, and there are no special restrictions on this.

Referring to FIG. 1, the tubular reactor used in the present invention may include a multitube falling-film evavorator.

The above multitube falling-film evaporator can induce a faster and more effective decomposition reaction of melted waste plastic by forming a uniform temperature distribution inside a plurality of tubes.

In addition, the tubular reactor used in the present invention is characterized in that it includes multiple zones that are vertically separated, and performs thermal decomposition of waste plastic under conditions of increasing temperature from the upper zone to the lower zone of the tubular reactor. To this end, the present invention can be configured such that external heating jackets having different lengths are arranged in each zone in the tubular reactor including multiple zones, so that the waste plastic melt flowing in the direction of gravity in the reactor is heated to a relatively low temperature in the upper zone and to a relatively high temperature in the lower zone. In this case, since the vaporization of light oil in the liquid stream increases depending on the heating temperature, the ratio of light oil in the liquid stream decreases while descending from the upper zone to the lower zone, thereby increasing the viscosity. That is, the liquid stream staying in the upper zone exhibits low viscosity due to a relatively high ratio of light oil, and thus quickly descends in the direction of gravity, while the liquid stream in the lower zone slows down in its descending speed due to an increase in viscosity caused by a decrease in the ratio of solid oil.

Therefore, in order to secure a uniform and sufficient residence time according to the viscosity of the liquid stream in each zone of the tubular reactor and improve the pyrolysis efficiency, it is preferable to configure the length of the external heating jacket in each zone to be inversely proportional to the viscosity residing in the corresponding zone. Specifically, the length of the external heating jacket in the upper zone can be configured to be the longest and to become shorter as it goes toward the lower zone. For example, the length of the external heating jacket provided in the upper zone of the tubular reactor can be configured to be 1 to 2 times, specifically 1.2 to 1.8 times, the length of the lower jacket below it. If the length of the heating jacket in the upper zone is the same as or shorter than the length of the heating jacket in the lower zone, the liquid stream residing in the upper zone quickly descends due to its low viscosity, making it difficult to secure a sufficient pyrolysis time, and if it exceeds 2 times, the residence time in the upper zone, which maintains a relatively low temperature, becomes longer than necessary, and a gradual temperature increase effect due to the lowering of the fluid cannot be expected.

For example, as shown in Fig. 1, when the tubular reactor is divided into three zones Z1 to Z3 in the vertical direction and a separate external heating jacket is provided for each zone, the length ratio of the external heating jackets (Z1, Z2, and Z3) for each zone may be 5:3:2 or 4:3:2. This length ratio is not limited to the above numerical value, and may be adjusted according to the viscosity of the liquid stream remaining in each zone.

The above external heating jacket is a means for transferring heat to the waste plastic raw material. The waste plastic raw material can be heated by passing high temperature/high pressure steam, hot water or heat transfer fluid through the external jacket provided for each zone, and there is no special limitation on this.

Meanwhile, when waste plastic is pyrolyzed, C _1-4 gas components, C _5-12 light hydrocarbons such as naphtha, and longer-chain hydrocarbon components are vaporized and discharged to the top of the reactor, and high-viscosity residual wax is not vaporized and is discharged to the bottom of the reactor. If there are many high-boiling-point components among the vaporized upper discharge, the yield of high value-added light hydrocarbon oil is limited, and high-viscosity wax residues have low utility because they hinder process operation or cause a decline in the quality of the final product.

Accordingly, in order to increase the selectivity for conversion into light hydrocarbons during thermal decomposition of waste plastic, thermal decomposition in the tubular reactor can be performed under elevated temperature conditions in the range of 430 to 450°C.

Referring again to FIG. 1, when the tubular reactor includes three zones Z1 to Z3 in a vertical direction, when the uppermost zone (Z1) is heated to 430°C at a constant rate, for example, 5 to 20°C/min or 10 to 15°C/min, the plastic is evenly distributed on the inner surface of the tube as it descends and the temperature increases to cause pyrolysis, and the product vaporized by the pyrolysis can be discharged to the upper part of the reactor. Subsequently, when the middle zone (Z2) is heated to 440°C, the remaining liquid stream that was not vaporized in the uppermost zone (Z1) is further pyrolyzed, and the vaporized product can be discharged to the upper part of the reactor. Thereafter, when the lowermost zone (Z3) is heated to 450°C, the remaining liquid stream that was not vaporized in the intermediate zone (Z2) is further pyrolyzed, and the vaporized product can be discharged to the upper part of the reactor. At this time, discharge of the vaporized product can be performed by opening the vent valve of the reactor.

As explained above, since the vaporization of light oil in the liquid stream increases depending on the heating temperature of the waste plastic, the viscosity of the liquid stream increases from the upper zone to the lower zone during the stepwise temperature increase in the three zones. Therefore, it is desirable to configure the length of the external heating jacket for each zone to be inversely proportional to the viscosity residing in the corresponding zone so that the residence time of the liquid stream becomes uniform by considering the viscosity of each zone.

In addition, the temperature-elevated pyrolysis can improve the efficiency of the decomposition reaction of waste plastic by gradually increasing the reaction temperature in a specific temperature range where the decomposition reaction of waste plastic actively proceeds, thereby increasing the selectivity for conversion into light hydrocarbons compared to the pyrolysis at a single temperature. As a result, the yield of light hydrocarbon oil can be increased relative to the supply amount of waste plastic raw material, while minimizing the amount of wax remaining as a residue.

Meanwhile, considering that the raw material of the waste plastic is mainly a thermoplastic resin, for example, a mixture including polyethylene having a number average molecular weight of 10,000 to 500,000, specifically 100,000 to 300,000, or polypropylene having a number average molecular weight of 5,000 to 300,000, specifically 100,000 to 200,000, it is advantageous that the pyrolysis reaction is performed in a range of 430 to 450°C. When the pyrolysis temperature is less than 430°C, the pyrolysis rate may be slowed down, thereby decreasing the conversion into light hydrocarbons, and when it exceeds 450°C, the production of solid carbides such as char may increase due to overreaction caused by high heat.

In addition, the temperature-rising pyrolysis in the tubular reactor can also be performed in a linear temperature-rising manner, for example, at a temperature-rising rate of 0.1 to 0.2 °C/min in the range of 430 to 450 °C.

In one embodiment of the present invention, the thermal decomposition under the above temperature-elevated conditions can be performed for 1 to 3 hours. The thermal decomposition reaction time can be determined by considering the point in time at which the production rate of light hydrocarbons having 12 or less carbon atoms increases in each temperature range of 430 to 450° C. after the start of the decomposition reaction of the waste plastic.

Meanwhile, as shown in Fig. 2, the residue that is not thermally decomposed in the tubular reactor and is discharged to the bottom can be circulated to the upper supply port of the tubular reactor using a pump.

The gaseous stream generated by vaporization through thermal decomposition in each zone of the above tubular reactor may include C _1-4 hydrocarbons, C _5-12 hydrocarbons, C _13-22 hydrocarbons, and C _23-40 hydrocarbons.

Next, the gaseous stream generated in the thermal decomposition step is condensed to obtain liquid oil (S2).

The above condensation is a process for cooling the pyrolysis gas, thereby suppressing the polymerization reaction of hydrocarbons in the high-temperature pyrolysis gas discharged from the pyrolysis reactor and reducing the heat load of a subsequent process (purification process). For example, a gaseous stream discharged from the upper portion of the pyrolysis reactor may be supplied to a condenser and subjected to heat exchange with quench oil or quench water, thereby cooling and condensing to obtain liquid oil, and the liquid oil may be discharged from the lower portion of the condenser and transferred to a storage tank. Meanwhile, a gas component (e.g., C _1-4 hydrocarbon) that is not condensed in the heat exchange may be discharged from the upper portion and may be used as a heat source for a petrochemical process through a subsequent process such as compression.

The content of the liquid oil obtained through the above condensation is in the range of 80 to 95 wt% based on the weight of the waste plastic raw material, which means that the wax residue (residual wax) that is not decomposed due to high viscosity is discharged in a small amount of 20 wt% or less.

Specifically, the liquid oil may include a light oil (LO) of C _5-12 , a middle oil (MO) of C _13-22 , and a heavy oil (HO) of C _23-40 .

Among these, the content of light oil (LO) of C _5-12 , which can be used as high value-added fuel oil, may be 10 to 40 wt% of the weight of the liquid oil. In addition, the content of light oil (LO) of C _5-12 may be 10 to 50 wt% based on the weight of the waste plastic raw material before pyrolysis.

That is, in the present invention, by performing thermal decomposition of waste plastic under elevated temperature conditions in a tubular reactor including multiple zones separated vertically, the decomposition efficiency of waste plastic can be improved, thereby obtaining light oil (LO) of C _5-12 at a high yield.

Thereafter, the liquid oil is purified to separate the components (S3).

The liquid oil obtained through the above-mentioned elevated temperature thermal decomposition and condensation is a mixed oil containing light and longer-chain hydrocarbons, and therefore goes through a refining process in which it is supplied to a multi-stage distillation tower and separated step by step by boiling point difference.

The above purification process can be performed in a manner conventional in the art, and there are no special limitations. For example, the feed stream supplied to the distillation tower can include all light and heavy oil components obtained from the pyrolysis of waste plastic, and a stream including light hydrocarbons with low boiling points can be discharged from the top of the distillation tower, and a stream including heavy hydrocarbons with high boiling points can be discharged from the bottom of the distillation tower.

Meanwhile, when the temperature-elevated pyrolysis according to the present invention is performed in a plurality of pyrolysis reactors connected in series, the pipes connecting each reactor and the distillation tower can be connected to different positions to optimize the column operating heat capacity.

The feed stream supplied to the distillation tower may be a mixed oil including oil components obtained by pyrolysis of waste plastic, i.e., light oil (LO) of C _5-12 , medium oil (MO) of C _13-22 , and heavy oil (HO) of C _23-40 , and a stream including light components of C _5-12 may be separated and discharged from the top of the distillation tower.

In one embodiment of the present invention, the light C _5-12 hydrocarbons separated from the upper portion of the distillation tower may be in the range of 40 to 60 wt% of the total weight of the feed stream, i.e., the liquid oil (mixed oil), and may be in the range of 35 to 50 wt% based on the weight of the waste plastic raw material. The light C _5-12 hydrocarbons obtained in such a high yield can be usefully used as high-grade fuel oil through condensation.

In particular, the light hydrocarbon fuel oil of C _5-12 finally obtained in the present invention has a boiling point of 0 to 230°C, specifically 30 to 216°C, a kinematic viscosity at 40°C of 0.3 to 1.0 cSt, specifically 0.4 to 0.9 cSt, and a flash point of -80°C or higher (e.g., -40°C), and thus can be usefully used as a petrochemical raw material.

According to the present invention, by supplying waste plastic raw materials into a tubular reactor including multiple zones separated vertically and continuously performing thermal decomposition by gradually increasing the temperature toward the lower zones, the decomposition efficiency of waste plastics can be improved, thereby increasing the yield of high-grade light hydrocarbon oil and minimizing the discharge of residual wax having low utilization.

In addition, by considering the viscosity of the liquid component descending in each section of the tubular reactor, external heating jackets of different lengths are provided to secure sufficient reaction residence time, thereby further improving the thermal decomposition efficiency of waste plastic.

Furthermore, the utilization of light hydrocarbon fuel oil obtained from the pyrolysis of waste plastic can reduce greenhouse gas emissions caused by the supply of raw materials for petrochemical processes, and improve process efficiency such as reducing energy consumption. In addition, it is also environmentally beneficial because no harmful gases are generated during the treatment of waste plastic.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical idea of the present invention, and the scope of the present invention is not limited to these examples alone.

Example

Example 1 :

100 parts by weight of a waste plastic melt containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was prepared, and pyrolysis was performed under elevated temperature conditions at atmospheric pressure (1 bar) using a tubular reactor including three vertically separated zones Z1 to Z3 as shown in Fig. 1.

First, in the tubular reactor, the uppermost zone (Z1), the middle zone (Z2), and the lowermost zone (Z3) are each equipped with external heating jackets and heated to sequentially transfer heat of 430°C, 440°C, and 450°C, respectively, and the length ratio of the external heating jackets (Z1, Z2, and Z3) for each zone is configured as 4:3:2, and a plastic melt is injected into the upper supply port of the tubular reactor and pyrolysis is performed for 2 hours.

In the above tubular reactor, the plastic melt descends in the uppermost zone (Z1) heated to 430°C and is thermally decomposed on the inner surface of the tube, and the vaporized product is discharged to the top by opening the vent valve of the reactor. Subsequently, in the intermediate zone (Z2) heated to 440°C, the liquid stream that was not vaporized in the previous uppermost zone (Z1) is additionally thermally decomposed, and the vaporized product is discharged to the top of the reactor. Thereafter, in the lowermost zone (Z3) heated to 450°C, the remaining liquid stream that was not vaporized in the previous intermediate zone (Z2) is additionally thermally decomposed, and the vaporized product is discharged to the top of the reactor.

The upper discharge stream was introduced into a condenser connected to the tubular reactor, cooled to 25°C to obtain condensed liquid oil, and the uncondensed gas component was discharged.

The above liquid oil was supplied to a distillation tower and purified by separation according to boiling point, thereby finally producing C _5-12 light hydrocarbon pyrolysis oil.

Table 1 below shows the viscosity by temperature based on the intermediate component of the hydrocarbon contained in the liquid stream by zone, and using this, the viscosity of the liquid stream (mixed component) passing through each zone in the tubular reactor where the thermal decomposition reaction was performed was calculated and shown in Table 2.

In the above Table 2, it can be confirmed that as the heating temperature of the waste plastic increases from the upper zone to the lower zone of the tubular reactor, the vaporization of the light oil in the liquid stream increases, and thus the viscosity of the liquid stream increases. Therefore, it is desirable to configure the length of the external heating jacket for each zone to be inversely proportional to the viscosity residing in the corresponding zone so that the residence time of the liquid stream becomes uniform by considering the viscosity for each zone. That is, the length of the external heating jacket for each zone can be adjusted so as to satisfy the following mathematical expression 1.

[Mathematical formula 1]

H = 1/V -2.46

In the above mathematical expression 1,

H is the length (m) of the external heating jacket provided in each vertically separated section of the above tubular reactor,

V is the viscosity of the liquid component passing through each of the above zones (see Table 1).

Example 2 :

As shown in Fig. 2, the same process as in Example 1 was performed, except that the residue that was not thermally decomposed in the tubular reactor and was discharged to the bottom was circulated to the upper supply port of the tubular reactor using a pump.

Reference Example 1 :

100 parts by weight of waste plastic melt containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was supplied to a tubular reactor without compartmentalization, and pyrolysis was performed at atmospheric pressure (1 bar) and 430°C for 2 hours. The product vaporized by the pyrolysis was discharged to the top by opening the vent valve of the reactor.

The upper discharge stream was introduced into a condenser connected to the tubular reactor, cooled to 25°C to obtain condensed liquid oil, and the uncondensed gas component was discharged.

The above liquid oil was supplied to a distillation tower and purified by separation according to boiling point, thereby finally producing C _5-12 light hydrocarbon pyrolysis oil.

Reference Example 2 :

The same process as in Reference Example 1 was performed, except that thermal decomposition was performed at atmospheric pressure (1 bar) and 450°C in the above tubular reactor.

Comparative Example 1 :

100 parts by weight of a waste plastic melt containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was supplied to a stirred tank reactor, and a pyrolysis reaction was performed at atmospheric pressure (1 bar) and 430°C for 2 hours. The product vaporized by the pyrolysis was discharged to the top by opening the vent valve of the reactor.

The upper discharge stream was introduced into a condenser connected to the tubular reactor, cooled to 25°C to obtain condensed liquid oil, and the uncondensed gas component was discharged.

The above liquid oil was supplied to a distillation tower and purified by separation according to boiling point, thereby finally producing C _5-12 light hydrocarbon pyrolysis oil.

Comparative Example 2 :

The same process as in Comparative Example 1 was performed, except that thermal decomposition was performed at atmospheric pressure (1 bar) and 450°C in the above-mentioned stirred reactor.

The composition of the liquid oil obtained through condensation after pyrolysis of waste plastic in the above examples, reference examples and comparative examples was analyzed by GC-MS, and the fractions of non-condensable C _1-4 gas, condensed liquid oil (including light oil (LO) of C _5-12 , middle oil (MO) of C _13-22 and heavy oil (HO) of C _23-40 ), and residue were calculated using the peak area ratio by region according to carbon number in the mass spectrometry spectrum.

Table 3 below shows the fraction of LO (C _5-12 ) in liquid oil according to the thermal decomposition conditions and the yield of LO (C _5-12 ) relative to the amount of waste plastic raw material supplied.

In the above Table 3, it can be confirmed that Example 1, in which thermal decomposition of waste plastic was performed under elevated temperature conditions in the range of 430 to 450°C using a multi-zone tubular reactor, improved the fraction of liquid oil of light oil (LO) of C _5-12 and the yield based on the raw material supply amount compared to the reference example and the comparative example.

Specifically, Reference Examples 1 and 2 showed improved yields of light oil (LO) of C _5-12 compared to Comparative Examples 1 and 2 of the stirred reactor by using a tubular reactor, but showed unstable yield distributions of light hydrocarbons compared to Example 1 in which step-wise temperature-elevated pyrolysis was performed in multiple zones of the tubular reactor by pyrolysis at a single temperature.

Claims (14)

(S1) A step of thermally decomposing waste plastic raw materials by feeding them into the upper feed port of a tubular reactor including multiple vertically separated zones;
(S2) a step of condensing the gaseous stream generated in the above thermal decomposition step to obtain liquid oil; and
(S3) comprising a step of refining the liquid oil;
A method for producing waste plastic pyrolysis oil, wherein the above pyrolysis is performed under conditions where the temperature increases from the upper section to the lower section of the tubular reactor. In the first paragraph,
The above tubular reactor is a method for producing waste plastic pyrolysis oil including a multitube falling-film evavorator. In the first paragraph,
A method for producing waste plastic pyrolysis oil, wherein the gaseous stream generated by pyrolysis in the above step (S1) is discharged to the top of the tubular reactor, and the remaining liquid stream descends along the inner surface of the tubular reactor. In the third paragraph,
A method for producing waste plastic pyrolysis oil, wherein a liquid stream descending inside the tubular reactor exhibits increasing viscosity from the upper zone to the lower zone. In the first paragraph,
A method for producing waste plastic pyrolysis oil, wherein the tubular reactor is heated through an external jacket having different lengths for each zone, and the length of the external jacket becomes shorter from the upper zone to the lower zone, thereby controlling the residence time for each zone according to the increase in viscosity of the liquid stream. In paragraph 5,
A method for producing waste plastic pyrolysis oil, wherein the length of the external jacket provided in the upper section of the above tubular reactor is more than 1 to 2 times the length of the external jacket provided in the lower section therebelow. In the first paragraph,
A method for producing waste plastic pyrolysis oil, wherein in the above step (S1), pyrolysis is performed under elevated temperature conditions in the range of 430 to 450°C. In the first paragraph,
A method for producing waste plastic pyrolysis oil, wherein the residue that is not pyrolyzed in the above step (S1) and is discharged from the bottom of the tubular reactor is circulated to the upper supply port of the tubular reactor using a pump. In the first paragraph,
A method for producing waste plastic pyrolysis oil, wherein the liquid oil obtained in the above step (S2) is 80 to 95 wt% based on the weight of the waste plastic raw material. In the first paragraph,
A method for producing waste plastic pyrolysis oil, wherein the liquid oil obtained in the above step (S2) includes light oil (LO) of C _5-12 , middle oil (MO) of C _13-22 , and heavy oil (HO) of C _23-40 . In Article 9,
A method for producing waste plastic pyrolysis oil, wherein the content of the light oil (LO) of the above C _5-12 is 10 to 40 wt% of the weight of the liquid oil. In Article 9,
A method for producing waste plastic pyrolysis oil, wherein the content of the light oil (LO) of the above C _5-12 is 10 to 50 wt% based on the weight of the waste plastic raw material. In the first paragraph,
The above waste plastic raw material is a method for producing waste plastic pyrolysis oil, which is a mixture containing polyethylene (PE) and polypropylene (PP). In the first paragraph,
A method for producing waste plastic pyrolysis oil, wherein the waste plastic raw material is supplied to the tubular reactor after undergoing a pretreatment process including crushing, washing, drying and melting.